A disk drive system includes one or more magnetic recording disks and control mechanisms for storing data within approximately circular tracks on the disk. A disk is composed of a substrate and one or more layers deposited on the substrate (e.g., aluminum). A trend in the design of disk drive systems is to increase the recording density of the magnetic recording disk used in the system. One method for increasing recording density is to pattern the surface of the disk with discrete tracks, referred to as discrete track recording (DTR). A DTR pattern may be formed by nano-imprint lithography (NIL) techniques, in which a rigid, pre-embossed forming tool (a.k.a., stamper, embosser, etc.), having an inverse pattern to be imprinted, is pressed into an embossable film (i.e., polymer) disposed above a disk substrate to form an initial pattern of compressed areas. This initial pattern ultimately forms a pattern of raised and recessed areas. After stamping the embossable film, an etching process is used to transfer the pattern through the embossable film by removing the residual film in the compressed areas. After the imprint lithography process, another etching process may be used to form the pattern in a layer (e.g., substrate, nickel-phosphorous, soft magnetic layer, etc.) residing underneath the embossable film.
One prior DTR structure forms a pattern of concentric raised areas and recessed areas under a magnetic recording layer. The raised areas (also known as hills, lands, elevations, etc.) are used for storing data and the recessed areas (also known as troughs, valleys, grooves, etc.) provide inter-track isolation to reduce noise. The raised areas have a width less than the width of the recording head such that portions of the head extend over the recessed areas during operation. The recessed areas have a depth relative to fly height of a recording head and raised areas. The recessed areas are sufficiently distanced from the head to inhibit storage of data by the head in the magnetic layer directly below the recessed areas. The raised areas are sufficiently close to the head to enable the writing of data in the magnetic layer directly on the raised areas. Therefore, when data are written to the recoding medium, the raised areas correspond to the data tracks. The recessed areas isolate the raised areas (e.g., the data tracks) from one another, resulting in data tracks that are defined both physically and magnetically.
A DTR disk may not be viable if the imprinting surface is not concentrically aligned with the disk substrate. An imprinted track that has excessive offset from a centerline of the disk may not operate properly when read by a disk drive head. This requirement may be particularly important when data tracks are generated on both sides of the disk. As such, the imprinting of an embossable film above a disk substrate requires an alignment step, in which a centerline of the disk is aligned with a centerline of the imprinting surface, before the embossable film is actually imprinted.
Current alignment methods typically require the use of high precision actuators or robotics. For example, high precision actuators would first determine a centerline for the disk substrate and align it with a centerline of the imprinting surface through a high resolution X-Y translation procedure. FIG. 1 illustrates a conventional X-Y translation stage that includes flexures for gripping a disk. Flexures are widely used in precision machines because they may provide frictionless, particle-free and low maintenance operation, while providing high precision. However, flexure based systems have limited ranges of motion and may not be adequate to center a disk relative to the imprinting surface of a stamper. The translation stage allows heat to dissipate from the surface of the disk that may result in inconsistent imprint patterns. Moreover, the use of such high precision actuators and robotics are expensive, with high maintenance costs, inconsistent accuracy and reliability, slow cycle times, and mechanical breakdown. The high precision actuators and robotics are bulky pieces of machinery, requiring large amounts of floor space.